The railways Thursday began a probe into Monday's fire aboard Chennai-bound Tamil Nadu Express that killed 28 passengers in Andhra Pradesh.
Dinesh Kumar Singh, the commissioner of railway safety, south central circle, started the public inquiry at the Nellore railway station.
He recorded the statements of railway employees who were on duty at the time of the disaster and witnesses. The hearing will continue Friday.
For the third consecutive day, forensic experts examined the gutted S 11 coach.
The cause of the fire remained a mystery with some witnesses claiming that they heard an explosion before the flames engulfed the coach around 4.30 a.m. Monday.
Some district officials said short circuit in electric panels could have triggered the fire. Rail officials have not ruled out sabotage in view of suspicions on how huge flames engulfed the coach within minutes.
There was confusion on the number of victims. The authorities initially put the death toll at 32 but later said only 28 bodies were found from the ill-fated coach.
The officials have identified and handed over 21 bodies to their relatives and the remaining were kept at a hospital in Nellore.
With seven bodies reduced to ashes, the authorities are planning DNA test to identify them.